The overall objectives of this project are: 1. To determine the bactericidal power of neutrophils (PMN's) in children with leukemia. 2. To study the toxic effects of vincristine on PMN function. 3. To correct PMN dysfunctions in leukemia by metabolic and immunologic manipulations of PMN's in vitro. Our work during 1974-1975 established the existence of a bactericidal power defect in 50% of leukemic children during relapse. Decreased PMN NBT-reductase activity was observed in some relapse patients, without correlation with decreased bactericidal power. Phagocytosis was normal. Vincristine toxicity on PMN functions consisted of an antiphagocytic effect without effect on bactericical power. The continuation of that project will involve the following goals for the year 1975-1976: 1. We will accumulate a pool of additional leukemic patients with defective bactericidal power, who will be available for metabolic studies when they develop relapse later and will provide a source of dysfunctional PMN's for our attempts to correct defective bactericidal power with IgG-glucose oxidase conjugates. 2. We want to develop a model of PMN's with decreased bactericidal power, using phenylbutazone and hydrocortisone to inhibit PMN bactericidal power in vitro. 3. Purified rabbit IgG will be conjugated to glucose oxidase by diethylmalonimidation. We will use these conjugates to attempt the in vitro correction of defective bactericidal power in PMN's of patients with CGD, leukemia and in PMN's rendered dysfunctional with drugs. 4. We will further study the VCR-induced phagocytic defect using Stossel's paraffin oil kinetic technique, and VCR incubation conditions similar to the ones described in the original project.